Telegram, the high-security messaging app, has shut down 78 Islamic State-related channels. Here's a look at what the app is and why terrorists are using it. (Jhaan Elker/The Washington Post)

Pavel Durov knew that terrorists might be using his app to communicate. And he decided it was something he could live with.

“I think that privacy, ultimately, and our right for privacy is more important than our fear of bad things happening, like terrorism,” the founder of Telegram, a highly secure messaging app, said at a TechCrunch panel in September when asked if he “slept well at night” knowing his technology was used for violence.

“If you look at ISIS, yes, there’s a war going on in the Middle East,” he continued. “Ultimately, ISIS will find a way to communicate with its cells, and if any means doesn’t feel secure to them, they’ll [find something else]. We shouldn’t feel guilty about it. We’re still doing the right thing, protecting our users’ privacy.”

Even after the Islamic State used the app to claim responsibility for an attack that killed 129 and wounded more than 350 in Paris, the man known as “the Russian Mark Zuckerberg” was unswayed, BuzzFeed reported.

Some called for encrypted chat programs like Telegram to be banned, in light of reports that militants used the highly secure systems to communicate.

But Durov responded, “I propose banning words. There’s evidence that they’re being used by terrorists to communicate,” in a post on the Russian social networking site VKontakte (which he co-founded). In a Facebook post, Durov blamed “shortsighted socialists” in the French government for the attacks as much as Islamic State militants.

Which is why a statement from Telegram posted on its site Wednesday comes as something of a surprise.

“We were disturbed to learn that Telegram’s public channels were being used by ISIS to spread their propaganda,” it read. “… As a result, this week alone we blocked 78 ISIS-related channels across 12 languages.”

The statement had a ring of insincerity to it, given Durov’s comments two months ago. (The New York Times noted that the statement sounded like Claude Rains’s famous line in “Casablanca,” claiming to be “shocked, shocked” to find that gambling was happening at Rick’s, just before collecting his winnings.)

Telegram has two separate systems, Durov explained: a private chats (between individual users and groups) and a newer public “channel” feature. They are analogous to Twitter direct messages and public feeds.

Durov will not be cracking down on the encrypted private chats. But he will bar the public channels, which were reportedly being used by Islamic State supporters to distribute propaganda. In an email to The Post, Durov wrote that Telegram intended to block Islamic State-related public content on Telegram channels from the start — though

It’s a convoluted explanation — but one characteristic of Durov, a 31-year-old, vehemently pro-privacy Russian exile with a subversive streak and a penchant for black clothing.

Before Telegram, he and his brother Nikolai founded VKontakte, a social networking site more popular than Facebook in Russia. He drew national attention — and acrimony inside and outside the Russian government — for a rebellious insistence on doing things his way. Vehemently anti-regulation, he allowed VK users to upload videos and music for which they didn’t hold the copyright, a move that was slammed by trade organizations and the music industry. On Russia’s Victory Day, which celebrates the end of World War II, he tweeted, “67 years ago, Stalin defended from Hitler his right to suppress the people of the USSR.” Much of Russia did not find the joke funny.

His behavior can oscillate between odd and audacious. In one incident, he threw paper airplanes made of money out his window, then watched a fight break out over the cash on the street below. He also offered Edward Snowden a job when the former U.S. intelligence contractor was granted asylum in Russia.

But in another, more serious confrontation, he defied a demand from the Russian government that he remove the VK pages of opposition figures during disputed parliamentary elections in 2011. He tweeted his “official response”: a photo of a dog sticking out its tongue.

Not long after, he found his home in St. Petersburg surrounded by a SWAT team, according to the New York Times. He wouldn’t open the door, and eventually they went home. But the incident convinced him of the need for an encrypted messaging system he could use to communicate in a scenario like that one. It was the inspiration for Telegram.

Durov’s anti-regulation, pro-privacy stance eventually cost him. In 2013, he became the target of a criminal investigation after he was accused of driving over a policeman’s foot, according to Mashable. Durov claimed the alleged crime never happened, and the investigation was politically motivated.

The Kremlin “was coming after me,” he said.

The Islamic State and its supporters use social media to post propaganda and recruit followers. The Washington Post takes a closer look at how several groups in the U.S. monitor this activity. (Gillian Brockell and Jorge Ribas/The Washington Post)

Then two original VKontakte investors sold their shares, representing 48 percent of the company, to an investment firm with close ties to the Kremlin.

Finally, in April 2014, amid increased pressure to release the data of Ukrainian protesters using his site, Durov gave up, according to the New York Times. He sold his shares and fled Russia.

Telegram was initially released in 2013 and its channel service was launched this September. Designed to protect members’ anonymity, the app allows users to send encrypted messages and establish “channels” of hundreds of followers without providing any information on their real identities other than a phone number, for which any phone can be used. That makes it all but impossible for law enforcement agencies to track them — which is exactly the point, Durov says.

But it also makes the app attractive to extremist groups. In an Oct. 29 report, the Middle East Media Research Institute warned that the app’s channel and chat feature would become a “fertile and secure arena for jihad-related activities.”

Charlie Winter, a senior researcher at the Quilliam Foundation, a research organization in the United Kingdom, told The Washington Post in October that he’d seen an Islamic State follower post, “Twitter can suspend me 1,000 times but I will always be on Telegram.”

While tech companies like Twitter and YouTube have been active in shutting down Islamic State-associated accounts and removing gruesome or violent propaganda images, until Telegram has been generally opposed to doing the same.

When M. Khayat, the author of the Middle East Media Research Institute report, reached out to ask about these policies, Telegram responded by saying that its channels are the “private territory of their respective participants and we do not process any requests related to them,” he told The Post.

This contrasts with Durov’s assertion in an email to The Post that Telegram intended to block Islamic State-related public content on Telegram channels from the start.

“There was no sudden change in our approach,” he said.

In a statement about Telegram channels released shortly after the first on Wednesday, the app rushed to clarify that the move wouldn’t apply to any types of banned speech.

“For example, if criticizing the government is illegal in a country, Telegram won’t be a part of such politically motivated censorship,” it read. “While we do block terrorist (e.g. ISIS-related) bots and channels, we will not block anybody who peacefully expresses alternative opinions.”

Not long after, Telegram’s (former) Islamic State users took to the site to express their outrage. “The war on Telegram has started,” one wrote, according to Winter.